Make the Items property of your gallery: (Filter(Filter(colMRQ,Status<>"Completed"), IsBlank(Assigned_To_1) || Assigned_To_1= User().FullName)) // This filters your new collection by Status first and then filters the result by Assigned_To_1 is blank or Assigned_To_1 is the current user. You may need to put User().FullName in quotes, I'm not sure about it so try it both ways to see which one works.

I tried to do this in the attached example using a Sharepoint list with >2000 rows. The Items property is shown in the box above the gallery. It filters a collection called docs that was ClearCollect(docs,Doctors) by whether the Middle initial (MI) is either blank or = "A." and then by Referring="True".

I tried to simplify the filter and this worked also: Filter(docs,IsBlank(MI) || MI="A.",Referring="True")